(a) Technical Field
The present invention relates to a variable differential mount apparatus. More particularly, it relates to a variable differential mount apparatus using a Magnetorheological Elastomer (MRE), which can secure riding comfort and handling stability through reversible and instant variation of the characteristics in accordance with a specific driving condition of a vehicle.
(b) Background Art
A differential is a torque transmission device typically made up of gears that offsets a difference between speed of an inner wheel and an outer wheel while a vehicle is making a corner. As the speed or rotation ratio of both wheels is controlled by the differential, both wheels can smoothly rotate without sliding when a vehicle makes a corner. Thus, the differential allows each of the driving wheels to rotate at different speeds. Therefore, the differential receives one input and provides two outputs.
Differentials are typically installed in vehicles to divide and transmit a torque provided by a drive shaft to both driving wheels and control the rotational speed of both the wheels accordingly. The following description of a differential applies to a “traditional” rear-wheel-drive car or truck with an “open” or limited slip differential combined with a reduction gear set:
For example, in a rear wheel drive car, torque is supplied from the engine, via the transmission, to a drive shaft/‘propeller shaft’, which runs to a final drive unit that contains the differential. A spiral bevel pinion gear is supplied a drive from the end of the propeller shaft, and is encased within the housing of the final drive unit which contains a plurality of gears that output two separate torque to each of the rear wheels respectively. FIG. 11 is a front view illustrating a typical differential mounting structure.
The typical differential mounting structure includes a mounting bracket 114 having a cylindrical shape and fixed on a subframe 112, an insulator 116 mounted in the mounting bracket 114, a mounting bush 118 press-fitted into the center of the insulator 116, and a differential supporting shaft 110 fitted into the mounting bush 118.
Here, the insulator 116 may be formed of a rubber material, and a gap 122 may be formed around the circumferential surface thereof to increase the shock-absorbing performance. Thus, in the typical differential mounting structure, vertical and horizontal vibrations, i.e., vibrations caused by compression delivered from an engine through a propeller shaft are absorbed by the insulator 116, and are prevented from being delivered to the body of a vehicle.
During cornering, a rubber mount of higher stiffness may be used to increase handling stability. However, a higher stiffness of the rubber mount generally causes lower riding comfort for the passengers and driver.
In the case of a typical differential mount apparatus, since the characteristics of a member such as a rubber mount inserted to support are limited, there is no choice but to provide limited riding comfort and handling stability due to the limited characteristics of the member in spite of variable driving conditions. Accordingly, a differential mount apparatus for improving both riding comfort and handling stability is needed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.